A water treatment method using an advanced oxidation process (AOP) is directed to a technology which generates an OH radical (OH°, Hydroxy radical) having a strong sanitization and oxidizing power as an intermediate material by using an oxidation agent such as ozone or H2O2 or by scanning a ultraviolet rat to the oxidation agent for thereby oxidizing and decomposing an organic pollutant in a waste water. The above water treatment method is an advanced technology which is used to decompose a undecomposable substance such as a synthetic washing agent, agricultural chemical, etc. which are not well decomposed by a common treatment method and is used to decompose a high concentration pollutant for a short time period. In recent years, as an environment pollution becomes a serious problem, and a new material, which cannot be decomposed by a common treatment method, is developed, a new technology is needed with respect to a waste treatment method which has an excellent process efficiency as a lot of undecomposable substance is inputted into a waste water. In addition, according to the amended law in the Korean law, it became a duty matter that a heavy water facility is installed in an architecture having a certain dimension. In case of a city building which is hard to adapt a biochemical treatment method, and in case of a conventional factory which is hard to increase a treatment capacity of a waste water, and in case that a lot of waste water should be treated in a limited treatment space, the application of a water treatment method using an advanced oxidation is widened, which has a high treatment efficiency of a waste water and is able to treat a lot of water for a short time without bad smell in a small area.
In recent years, various trials are conducted for enhancing a decomposition efficiency of an advanced oxidation process. A multiple reaction tub may be installed so as to enhance a contact surface area of ozone. According to a DOF (Dissolved Ozone Flotation) method, ozone is compressed using a compressor so as to enhance solubility and is inputted into a waste water which is pressurized with a high pressure and is discharged to a waste water with a normal pressure for thereby forming ozone foams and floating the same. The pollutant and micro ozone are reacted with each other. According to the DOF, it is possible to obtain a less size foam and a larger size surface area as compared to when foam is generated by means of a conventional ejector. So, it is possible to increase decomposition reaction efficiency as a contact efficiency of ozone increases.
In addition, there is a method for inducing a decomposition reaction of ozone in an area near a lamp in consideration with a characteristic of an ultraviolet ray (254 nm) having a low water penetration power as an ultraviolet ray is scanned so as to increase a decomposition efficiency of ozone, a porous plate is installed near an ultraviolet lamp, and ozone passes through near a lamp. In the above operation, it is expected that a decomposition reaction efficiency is enhanced based on an OH radical generated as a photocatalyst scanned by an ultraviolet ray decomposes ozone by coating a photocatalyst on the porous plate. The water treatment apparatus and method using an advanced oxidation process is disclosed in the Korean patent laid-open number 109288, the patent registration number 289275 and the patent registration number 541573.
However, the above patents have the problems. Namely, the Korean patent registration number 109288 and the patent registration number 289275 disclose the DOF in which the ozone is pressurized using a compressor so as to purify waste water, and the pressurized ozone is inputted into the waste water which was pressurized using a pump and is dissolved, and is inputted into waste water under normal pressure for thereby generating a micro foam ozone and increasing the contact surface. In the above method, it is possible to enhance a decomposition reaction efficiency as the contact surface area increases with respect to the pollutant with small size foams as compared to the floating method by means of an ejector having relatively large foams, but the amount of the ozone to be dissolved under water under the normal pressure is very limited, so that almost ozone inputted remain in a foam type, and the decomposition reaction of the ozone and pollutant is performed via a gas-liquid surface. Therefore, the reaction speed is slow. As the pollutant foam size decreases, the contact surface area increases, so that the decomposition reaction speed may slightly increase. However, since the inputted ozone is fast floated above the water and escapes, the amount of the gaseous ozone is relatively less, so that there is a limit for enhancing the reaction efficiency.
The conventional advanced oxidation process is related with a technology which decreases the sizes of foams. The method for treating the waste water based on the DOF which performs a reaction almost via a gas-liquid surface is performed using an inherent oxidation power of ozone which is able to oxidize and decompose almost organic pollutants by enhancing a contact efficiency between ozone and pollutant. The above method is faster than a biological decomposition method. In a lot of pollutants, the decomposition reaction speed is disadvantageously slow, and the volume of the reaction apparatus disadvantageously decreases. There are substances which do not react, and a lot of undecomposable substance such as agricultural chemicals, synthetic washing agent, etc. may be inputted into sewage or waste water, so that there are limits for treating the above water problems with only ozone.
So as to improve the disadvantages of the ozone, ozone is decomposed by concurrently reacting oxidizing agent such as H2O2 and ultraviolet ray for thereby creating an OH radical having a strong oxidizing power. As a method for decomposing pollutants based on the created OH radical, there is an advanced oxidation process such as ozone+H2O2, ozone+ultraviolet ray, ozone+photocatalyst+ultraviolet ray, ozone+photocatalyst+ultraviolet ray, ozone+ultrasonic wave, etc.
The Korean patent registration number 541573 discloses a method for an advanced oxidation process which uses ozone+photocatalyst+ultraviolet ray in which ozone is inputted via a lower side of the reactor and is dispersed via a porous plate formed at a surrounding portion of an ultraviolet lamp and is decomposed, so that a decomposition reaction is performed based on a photocatalyst coated on the surface of the porous hole. Since the inputted ozone is present in a foam state, as the input amount of ozone increases, the amount of foams increases for thereby retarding the irradiation of ultraviolet ray, and the size of ozone foam increases, so that the contact efficiency with the pollutant decreases, and the creating amount of the OH radical generated based on the decrease of the oxidation reaction and by means of a reaction of the ultraviolet ray. In the above patents, there is provided a water treatment apparatus which has a porous plate coated with a photocatalyst through which the ultraviolet lamp passes so as to enhance a reaction between the ozone and the ultraviolet ray. However, the number of the porous plate is limited for the reason of the pressure loss. It is impossible to increase the creation of the OH radical based on an ultraviolet ray decomposition reaction and a photocatalyst reaction owing to the retardation of the ultraviolet ray scanning due to the ozone foams. As a result, the surface area of the photocatalyst coating cannot increase owing to the increasing pressure loss by means of the installed porous plate, so that there is a limit in the presses capacity. Namely, there is a limit for enhancing the decomposition reaction efficiency since the solubility of the ozone inputted in a foam shape, and the transmission of the ultraviolet is interfered.
In the advanced oxidation process using a conventional DOF, the ozone is pressurized to a high level using the compressor, and the waste water is pressurized using a pressurizing pump, and a high pressure ozone is inputted into the waste water and is dissolved and then is discharged with a normal pressure, so that a micro size ozone foam is generated and is floated upward for thereby along the floating substance to move up and react with the pollutant, whereby the pollutant are removed. The water treatment method based on the DAF (Dissolved Air Flotation) and the DOF (Dissolved Ozone Flotation) are disclosed in the Korean patent laid-open number 10-2006-0026698, the Korean patent laid-open number 10-2005-0109288, the Korean patent registration number 0321800, and the Korean patent registration number 0420561. In the floating substance and pollutant removing method using the micro size foam type air or ozone floatation, the waste water is sucked and compressed by means of the pressure pump, and the ozone generated by the air and ozone generator is compressed by means of the compressor and is forcibly inputted into a high pressure waste water and is dissolved. A method of using an exclusive pump, for example, a DAF pump is considered.
In the air flotation method, the floating substance contacts with micro foams and is floated upward for thereby removing the same. A lot of air is dissolved with a high pressure so as to enhance the efficiency of the air floatation method and is inputted into a waste water of a normal pressure for thereby forming micro foams. In a method for enhancing a floating substance removing efficiency, a specially designed DAF exclusive pump may be used, and a high pressure air compressed using the compressor is mixed and dissolved by means of a high pressure waste water pressurized by the pressurizing pump and is inputted into a floatation tub. However, in this method, an air compression compressor or an exclusive DAF pump is disadvantageously needed.
In the conventional advanced oxidation process, since unreacted ozone is properly not used, but is just discharged into the air or it is decomposed using a decomposition apparatus and is discharged, the use efficiency of the ozone is very low. Since an expensive ozone generator is used, and a cost is increased since it is needed to increase a capacity of a unreacted ozone decomposition apparatus. The apparatus needed for an advanced oxidation process should be big so as to increase the contact area needed for enhancing a decomposition reaction efficiency of a pollutant, so that an installation and operation cost increases.
In addition, almost ozone is not properly used since a technology related with a pollutant removing process using a conventional advanced oxidation process adapts a unreliable treatment method with respect to a unreacted ozone. Namely, such ozone is directly discharged into the air or is simply decomposed using an off-gas ozone decomposition apparatus. Since an ozone generator is expensive, it is impossible to expect a high application of the ozone because the ozone is generated using an expensive apparatus. An environmental problem may occur, and an installation cost and an operation cost are too high.